parser/
stmt.rs

1use crate::try_parse;
2use dynamic::{Dynamic, Type};
3
4use super::{Expr, Parser, Pattern, Span, expr::ExprKind, pattern::PatternKind};
5use anyhow::{Result, anyhow};
6use smol_str::SmolStr;
7
8/// 把 pattern 引入的所有变量绑定生成出来,追加到 `out`。
9/// `access` 是该 pattern 整体对应的访问表达式(如 `__m_scrut` 或 `__m_scrut.field`)。
10fn collect_bindings(pat: &Pattern, access: &Expr, out: &mut Vec<Stmt>, span: Span) {
11    use crate::expr::BinaryOp;
12    let mk_let_ident = |name: SmolStr, value: Expr, span: Span| {
13        let p = Pattern::new(PatternKind::Ident { name, ty: Type::Any }, span);
14        let value_stmt = Stmt::new(StmtKind::Expr(value, true), span);
15        Stmt::new(StmtKind::Let { pat: p, value: Box::new(value_stmt) }, span)
16    };
17    let mk_bin = |left: Expr, op: BinaryOp, right: Expr, span: Span| Expr::new(ExprKind::Binary { left: Box::new(left), op, right: Box::new(right) }, span);
18    let mk_idx_int = |obj: Expr, i: i32, span: Span| mk_bin(obj, BinaryOp::Idx, Expr::new(ExprKind::Value(Dynamic::I32(i)), span), span);
19    let mk_field = |obj: Expr, name: SmolStr, span: Span| mk_bin(obj, BinaryOp::Idx, Expr::new(ExprKind::Value(Dynamic::String(name)), span), span);
20
21    match &pat.kind {
22        PatternKind::Ident { name, .. } => {
23            out.push(mk_let_ident(name.clone(), access.clone(), span));
24        }
25        PatternKind::Tuple(items) => {
26            for (i, p) in items.iter().enumerate() {
27                let elem = mk_idx_int(access.clone(), i as i32, span);
28                collect_bindings(p, &elem, out, span);
29            }
30        }
31        PatternKind::List { elems, has_rest } => {
32            let prefix = if *has_rest { elems.len() - 1 } else { elems.len() };
33            for (i, p) in elems.iter().take(prefix).enumerate() {
34                let elem = mk_idx_int(access.clone(), i as i32, span);
35                collect_bindings(p, &elem, out, span);
36            }
37            if *has_rest {
38                if let PatternKind::Ident { name, .. } = &elems.last().unwrap().kind {
39                    // 切片: access[prefix..];用 `ExprKind::Range` 而不是 `Binary{RangeOpen}`,
40                    // 与 parser 产物一致,这样下游 type infer / 优化都走同一条路径。
41                    let from = Expr::new(ExprKind::Value((prefix as u32).into()), span);
42                    let range = Expr::new(ExprKind::Range { start: Box::new(from), stop: Box::new(Expr::new(ExprKind::Value(Dynamic::Null), span)), inclusive: false }, span);
43                    let slice = Expr::new(ExprKind::Binary { left: Box::new(access.clone()), op: BinaryOp::Idx, right: Box::new(range) }, span);
44                    out.push(mk_let_ident(name.clone(), slice, span));
45                }
46            }
47        }
48        PatternKind::Struct { fields, .. } => {
49            for (fname, sub) in fields {
50                let field_access = mk_field(access.clone(), fname.clone(), span);
51                match sub {
52                    None => {
53                        // 简写 `field` —— 绑定同名变量
54                        out.push(mk_let_ident(fname.clone(), field_access, span));
55                    }
56                    Some(sub_pat) => {
57                        collect_bindings(sub_pat, &field_access, out, span);
58                    }
59                }
60            }
61        }
62        // 其它(Wildcard / Literal / Var / Member / Idx)在 match 上下文中不产生绑定
63        _ => {}
64    }
65}
66
67#[derive(Debug, Clone)]
68pub struct Stmt {
69    pub kind: StmtKind,
70    pub span: Span,
71}
72
73#[derive(Debug, Clone)]
74pub enum StmtKind {
75    Let { pat: Pattern, value: Box<Stmt> },
76    Expr(Expr, bool),
77    Block(Vec<Stmt>),
78    Break,
79    Continue,
80    Return(Option<Expr>),
81    While { cond: Expr, body: Box<Stmt> },
82    Loop(Box<Stmt>),
83    For { pat: Pattern, range: Expr, body: Box<Stmt> },
84    Fn { name: SmolStr, generic_params: Vec<Type>, args: Vec<(SmolStr, Type)>, body: Box<Stmt>, is_pub: bool },
85    Struct { name: SmolStr, def: Type, is_pub: bool },
86    Impl { target: Type, body: Box<Stmt> },
87    If { cond: Expr, then_body: Box<Stmt>, else_body: Option<Box<Stmt>> },
88    Static { name: SmolStr, ty: Type, value: Option<Expr>, is_pub: bool },
89    Import { module: SmolStr, path: SmolStr, is_pub: bool },
90    Const { name: SmolStr, ty: Type, value: Expr, is_pub: bool },
91}
92
93impl Stmt {
94    pub fn new(kind: StmtKind, span: Span) -> Self {
95        Self { kind, span }
96    }
97
98    pub fn expr(&self) -> Option<Expr> {
99        if let StmtKind::Expr(expr, _) = &self.kind { Some(expr.clone()) } else { None }
100    }
101
102    pub fn is_return(&self) -> bool {
103        matches!(self.kind, StmtKind::Return(_))
104    }
105
106    pub fn last_return(&mut self) -> bool {
107        match &mut self.kind {
108            StmtKind::Block(stmts) => stmts.last_mut().map(|stmt| stmt.last_return()).unwrap_or(false),
109            StmtKind::If { then_body, else_body, .. } => {
110                let then_returns = then_body.last_return();
111                let else_returns = else_body.as_mut().map(|body| body.last_return()).unwrap_or(false);
112                then_returns && else_returns
113            }
114            StmtKind::Expr(e, close) => {
115                if !*close {
116                    let span = e.span;
117                    *self = Self::new(StmtKind::Return(Some(std::mem::take(e))), span);
118                    true
119                } else {
120                    false
121                }
122            }
123            StmtKind::Return(_) => true,
124            _ => false,
125        }
126    }
127
128    pub fn get_type(&self) -> Option<Type> {
129        match &self.kind {
130            StmtKind::Expr(expr, _) => Some(expr.get_type()),
131            StmtKind::Block(stmts) => stmts.last().and_then(|stmt| stmt.get_type()),
132            StmtKind::If { then_body, .. } => then_body.get_type(),
133            _ => None,
134        }
135    }
136
137    fn get_assign(idx: u32, expr: Expr) -> Self {
138        let span = expr.span;
139        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(Expr::new(ExprKind::Var(idx), span)), op: crate::BinaryOp::Assign, right: Box::new(expr) }, span), true), span)
140    }
141
142    fn get_idx_assign(pat: Expr, idx: usize, expr: Expr) -> Self {
143        let span = pat.span.merge(expr.span);
144        let right = Expr::new(ExprKind::Binary { left: Box::new(expr), op: crate::BinaryOp::Idx, right: Box::new(Expr::new(ExprKind::Value((idx as u32).into()), span)) }, span);
145        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(pat), op: crate::BinaryOp::Assign, right: Box::new(right) }, span), true), span)
146    }
147
148    /// 与 `get_idx_assign` 类似,但把右侧索引读取包成 `Typed { value, ty }`。
149    /// 解构生成的 `arr[i]` 默认返回 `Any`(指向 Dynamic 的指针),
150    /// 不加类型标注的话元素槽会被声明成 Any,后续读取拿到的是裸指针而不是值。
151    /// 这里按模式里推导出的元素类型 `ty` 包一层 `Typed`,让 JIT 走 Any→ty 的转换。
152    fn get_idx_assign_typed(pat: Expr, idx: usize, expr: Expr, ty: Type) -> Self {
153        let span = pat.span.merge(expr.span);
154        let idx_expr = Expr::new(ExprKind::Binary { left: Box::new(expr), op: crate::BinaryOp::Idx, right: Box::new(Expr::new(ExprKind::Value((idx as u32).into()), span)) }, span);
155        let right = Expr::new(ExprKind::Typed { value: Box::new(idx_expr), ty }, span);
156        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(pat), op: crate::BinaryOp::Assign, right: Box::new(right) }, span), true), span)
157    }
158
159    fn get_assign_expr(pat: Expr, expr: Expr) -> Self {
160        let span = pat.span.merge(expr.span);
161        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(pat), op: crate::BinaryOp::Assign, right: Box::new(expr) }, span), true), span)
162    }
163
164    fn var_expr_with_ty(pat: &Pattern) -> Option<(Expr, Type)> {
165        if let PatternKind::Var { idx, ty } = &pat.kind
166            && !ty.is_any()
167        {
168            Some((Expr::new(ExprKind::Var(*idx), pat.span), ty.clone()))
169        } else {
170            None
171        }
172    }
173
174    pub fn bind_pattern(&mut self, pat: Pattern) -> Result<()> {
175        if let Some(expr) = self.expr() {
176            let stmt = match pat.kind {
177                PatternKind::Var { idx, ty } => {
178                    if expr.get_type() != ty {
179                        Self::get_assign(idx, Expr::new(ExprKind::Typed { value: Box::new(expr), ty }, pat.span))
180                    } else {
181                        Self::get_assign(idx, expr)
182                    }
183                }
184                PatternKind::Tuple(list) => {
185                    let mut stmts = Vec::new();
186                    for (idx, p) in list.into_iter().enumerate() {
187                        match Self::var_expr_with_ty(&p) {
188                            Some((p, ty)) => stmts.push(Self::get_idx_assign_typed(p, idx, expr.clone(), ty)),
189                            None => match p.expr() {
190                                Ok(p) => stmts.push(Self::get_idx_assign(p, idx, expr.clone())),
191                                Err(e) => return Err(e),
192                            },
193                        }
194                    }
195                    Self::new(StmtKind::Block(stmts), self.span)
196                }
197                PatternKind::List { elems, has_rest } => {
198                    let mut stmts = Vec::new();
199                    let prefix_count = if has_rest { elems.len() - 1 } else { elems.len() };
200                    if has_rest {
201                        for (idx, p) in elems.iter().take(prefix_count).enumerate() {
202                            match Self::var_expr_with_ty(p) {
203                                Some((p, ty)) => stmts.push(Self::get_idx_assign_typed(p, idx, expr.clone(), ty)),
204                                None => match p.expr() {
205                                    Ok(p) => stmts.push(Self::get_idx_assign(p, idx, expr.clone())),
206                                    Err(e) => return Err(e),
207                                },
208                            }
209                        }
210                    } else {
211                        for (idx, p) in elems.iter().enumerate() {
212                            match Self::var_expr_with_ty(p) {
213                                Some((p, ty)) => stmts.push(Self::get_idx_assign_typed(p, idx, expr.clone(), ty)),
214                                None => match p.expr() {
215                                    Ok(p) => stmts.push(Self::get_idx_assign(p, idx, expr.clone())),
216                                    Err(e) => return Err(e),
217                                },
218                            }
219                        }
220                    }
221                    if has_rest {
222                        // 最后一个元素是 `..rest`,把它绑定为 expr[prefix_count..] 的切片。
223                        let rest_pat = elems.last().unwrap();
224                        let rest_expr = match &rest_pat.kind {
225                            PatternKind::Ident { name, .. } => Expr::new(ExprKind::Ident(name.clone()), rest_pat.span),
226                            PatternKind::Var { idx, .. } => Expr::new(ExprKind::Var(*idx), rest_pat.span),
227                            _ => return Err(anyhow!("..rest 后的模式必须是标识符")),
228                        };
229                        let from = Expr::new(ExprKind::Value((prefix_count as u32).into()), rest_pat.span);
230                        // 用 `ExprKind::Range` 与 parser 产物对齐,确保下游 type infer 走切片分支。
231                        let range = Expr::new(ExprKind::Range { start: Box::new(from), stop: Box::new(Expr::new(ExprKind::Value(Dynamic::Null), rest_pat.span)), inclusive: false }, rest_pat.span);
232                        let slice_idx = Expr::new(ExprKind::Binary { left: Box::new(expr.clone()), op: crate::BinaryOp::Idx, right: Box::new(range) }, rest_pat.span);
233                        stmts.push(Self::get_assign_expr(rest_expr, slice_idx));
234                    }
235                    Self::new(StmtKind::Block(stmts), self.span)
236                }
237                p => return Err(anyhow!("不支持的模式绑定: {:?}", p)),
238            };
239            let _ = std::mem::replace(self, stmt);
240        } else {
241            match &mut self.kind {
242                StmtKind::Block(stmts) => {
243                    if let Some(stmt) = stmts.last_mut() {
244                        stmt.bind_pattern(pat)?;
245                    }
246                }
247                StmtKind::If { then_body, else_body, .. } => {
248                    then_body.bind_pattern(pat.clone())?;
249                    if let Some(e) = else_body {
250                        e.bind_pattern(pat)?;
251                    }
252                }
253                _ => {}
254            }
255        }
256        Ok(())
257    }
258}
259
260use std::fmt;
261impl fmt::Display for Stmt {
262    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
263        match &self.kind {
264            StmtKind::Let { pat, value } => writeln!(f, "let {:?} = {}", pat, value)?,
265            StmtKind::Block(stmts) => stmts.iter().for_each(|s| {
266                let _ = write!(f, "{}", s);
267            }),
268            StmtKind::Expr(expr, close) => writeln!(f, "{:?}[{}]", expr, close)?,
269            StmtKind::Break => writeln!(f, "break")?,
270            StmtKind::Continue => writeln!(f, "continue")?,
271            StmtKind::Return(r) => writeln!(f, "return {:?}", r)?,
272            StmtKind::While { cond, body } => write!(f, "while {:?}\n{}", cond, body)?,
273            StmtKind::Loop(body) => write!(f, "loop\n{}", body)?,
274            StmtKind::For { pat, range, body } => writeln!(f, "for {:?} in {:?} \n{}", pat, range, body)?,
275            StmtKind::If { cond, then_body, else_body } => {
276                write!(f, "if {:?}\nthen-> {}\n", cond, then_body)?;
277                if let Some(e) = else_body {
278                    writeln!(f, "{}", e)?;
279                }
280            }
281            StmtKind::Fn { name, generic_params, args, body, is_pub } => {
282                let generic_suffix = if generic_params.is_empty() { String::new() } else { format!("<{:?}>", generic_params) };
283                if *is_pub {
284                    write!(f, "pub fn {:?}{} {:?}\n", name, generic_suffix, args)?
285                } else {
286                    write!(f, "fn {:?}{} {:?}\n", name, generic_suffix, args)?
287                }
288                write!(f, "{}", body)?;
289            }
290            StmtKind::Import { module, path, is_pub } => {
291                if *is_pub {
292                    writeln!(f, "pub import {:?}, {:?};", module, path)?
293                } else {
294                    writeln!(f, "import {:?}, {:?};", module, path)?
295                }
296            }
297            _ => write!(f, "(todo display: {:?})", self.kind)?,
298        }
299        fmt::Result::Ok(())
300    }
301}
302
303impl Parser {
304    pub fn ident_typed(&mut self) -> Result<(SmolStr, Type)> {
305        let name = self.ident()?;
306        self.whitespace()?;
307        if self.take(b':').is_ok() { Ok((name, self.get_type()?)) } else { Ok((name, Type::Any)) }
308    }
309
310    pub fn ident_generic(&mut self) -> Result<(SmolStr, Vec<Type>)> {
311        self.whitespace()?;
312        let name = self.ident()?;
313        self.whitespace()?;
314        let params = if self.get()? == b'<' {
315            self.pos += 1;
316            crate::parse_list!(self, Vec::new(), b'>', b',', self.get_type_param()?)
317        } else {
318            Vec::new()
319        };
320        Ok((name, params))
321    }
322
323    pub fn block(&mut self) -> Result<Stmt> {
324        self.check_fatal()?;
325        self.whitespace()?;
326        let start = self.current_pos();
327        if self.get()? == b'{' {
328            self.pos += 1;
329            self.enter_depth()?;
330            self.push_decl_scope();
331            let result = (|| -> Result<Stmt> {
332                let body = crate::parse_list!(self, Vec::new(), b'}', 0, self.stmt(false)?);
333                Ok(Stmt::new(StmtKind::Block(body), self.span_from(start)))
334            })();
335            self.pop_decl_scope();
336            self.exit_depth();
337            result
338        } else {
339            Err(anyhow!("not code block"))
340        }
341    }
342
343    pub fn if_block(&mut self) -> Result<Stmt> {
344        let start = self.spans.last().copied().unwrap_or_else(|| self.current_pos());
345        let cond = self.get_expr_without_struct_literal()?;
346        let then_body = Box::new(self.block()?);
347        self.whitespace()?;
348        let else_body = if self.keyword("else").is_ok() {
349            self.whitespace()?;
350            let body = if self.keyword("if").is_ok() { self.if_block()? } else { self.block()? };
351            Some(Box::new(body))
352        } else {
353            None
354        };
355        Ok(Stmt::new(StmtKind::If { cond, then_body, else_body }, Span::new(start, self.current_pos())))
356    }
357
358    /// 解析 `match scrut { pat ("|" pat)* ("if" guard)? => body ","? ... }`,
359    /// desugar 成 `Block + Let + If 链 + 临时变量`,返回顶层 `Block`(再由
360    /// 调用方用 `ExprKind::Stmt` 包成表达式)。
361    pub fn match_block(&mut self, start: usize) -> Result<Stmt> {
362        use crate::expr::{BinaryOp, ExprKind, UnaryOp};
363        use crate::pattern::{Pattern, PatternKind};
364
365        // ---- 一、解析阶段 ----
366        let scrut = self.get_expr_without_struct_literal()?;
367        self.whitespace()?;
368        self.take(b'{').map_err(|_| anyhow!("match 缺少 `{{`"))?;
369
370        // 每个 arm 是 (pats: Vec<Pattern>, guard: Option<Expr>, body: Expr)
371        let mut arms: Vec<(Vec<Pattern>, Option<Expr>, Expr)> = Vec::new();
372        loop {
373            self.whitespace()?;
374            if self.take(b'}').is_ok() {
375                break;
376            }
377            self.push_decl_scope();
378            let arm_res: Result<(Vec<Pattern>, Option<Expr>, Expr)> = (|| {
379                // 一组 pattern(用 `|` 分隔,or-pattern)
380                let mut pats = vec![self.pattern()?];
381                self.whitespace()?;
382                while matches!(self.get(), Ok(b'|')) && !matches!(self.ahead(), Ok(b'|')) {
383                    self.pos += 1;
384                    self.whitespace()?;
385                    pats.push(self.pattern()?);
386                    self.whitespace()?;
387                }
388                // 声明 pattern 引入的变量(对每个 alt 都声明,允许重名 → 由
389                // declare_symbol_in_current_scope 容错;这里我们只用第一个 alt 的 binding)
390                for pat in &pats[..1] {
391                    self.declare_pattern_symbols(pat)?;
392                }
393                // 校验 or-pattern:第二及之后必须是 Literal(MVP 限制)
394                if pats.len() > 1 {
395                    for p in &pats[1..] {
396                        if !matches!(p.kind, PatternKind::Literal(_) | PatternKind::Wildcard) {
397                            return Err(anyhow!("or-pattern 中除第一个外只支持字面量 / 通配模式 (MVP 限制)"));
398                        }
399                    }
400                }
401                // 可选 guard
402                self.whitespace()?;
403                let guard = if self.keyword("if").is_ok() {
404                    self.whitespace()?;
405                    Some(self.get_expr_no_assign()?)
406                } else {
407                    None
408                };
409                // `=>`
410                self.whitespace()?;
411                self.just("=>").map_err(|_| anyhow!("match arm 缺少 `=>`"))?;
412                self.whitespace()?;
413                // 体
414                let body_start = self.current_pos();
415                let body = if self.get()? == b'{' {
416                    let block_stmt = self.block()?;
417                    Expr::new(ExprKind::Stmt(Box::new(block_stmt)), Span::new(body_start, self.current_pos()))
418                } else {
419                    // body 也用 no_assign 防止 `=> body, ...` 中 `,` 后或下一 arm
420                    // 的 `=>` 被错误吞入(同时仍允许 +-*/ 等正常二元)。
421                    self.get_expr_no_assign()?
422                };
423                // 容忍尾随逗号
424                self.whitespace()?;
425                let _ = self.take(b',');
426                Ok((pats, guard, body))
427            })();
428            self.pop_decl_scope();
429            arms.push(arm_res?);
430        }
431        let span = Span::new(start, self.current_pos());
432
433        // ---- 二、声明 match 顶层临时变量 ----
434        // 为避免嵌套 match 重名,加 counter 后缀(简单递增,parser 本地状态)
435        let suffix = self.match_counter;
436        self.match_counter += 1;
437        let scrut_name: SmolStr = format!("__m_scrut_{}", suffix).into();
438        let done_name: SmolStr = format!("__m_done_{}", suffix).into();
439        let out_name: SmolStr = format!("__m_out_{}", suffix).into();
440        self.declare_symbol_in_current_scope(&scrut_name)?;
441        self.declare_symbol_in_current_scope(&done_name)?;
442        self.declare_symbol_in_current_scope(&out_name)?;
443
444        // ---- 三、构建顶层 Block ----
445        let mk_ident = |name: &SmolStr, span: Span| Expr::new(ExprKind::Ident(name.clone()), span);
446        let mk_value = |v: Dynamic, span: Span| Expr::new(ExprKind::Value(v), span);
447        let mk_binary = |left: Expr, op: BinaryOp, right: Expr, span: Span| Expr::new(ExprKind::Binary { left: Box::new(left), op, right: Box::new(right) }, span);
448        let mk_let = |name: SmolStr, value: Expr, span: Span| {
449            let pat = Pattern::new(PatternKind::Ident { name, ty: Type::Any }, span);
450            let value_stmt = Stmt::new(StmtKind::Expr(value, true), span);
451            Stmt::new(StmtKind::Let { pat, value: Box::new(value_stmt) }, span)
452        };
453        let mk_assign_stmt = |name: &SmolStr, value: Expr, span: Span| {
454            let assign = mk_binary(mk_ident(name, span), BinaryOp::Assign, value, span);
455            Stmt::new(StmtKind::Expr(assign, true), span)
456        };
457        let mk_any = |value: Expr, span: Span| Expr::new(ExprKind::Typed { value: Box::new(value), ty: Type::Any }, span);
458
459        let mut stmts = Vec::new();
460        // let __m_scrut = SCRUT;
461        stmts.push(mk_let(scrut_name.clone(), scrut, span));
462        // let __m_done = false;
463        stmts.push(mk_let(done_name.clone(), mk_value(Dynamic::Bool(false), span), span));
464        // let __m_out = null;
465        stmts.push(mk_let(out_name.clone(), mk_value(Dynamic::Null, span), span));
466
467        // 每个 arm 一个 if(顺序构造)
468        for (pats, guard, body) in arms {
469            let arm_span = body.span;
470            let scrut_ident = mk_ident(&scrut_name, arm_span);
471            // test = pat[0].test || pat[1].test || ...
472            let mut test_chain = pats[0].match_test(&scrut_ident);
473            for p in &pats[1..] {
474                let t = p.match_test(&scrut_ident);
475                test_chain = mk_binary(test_chain, BinaryOp::Or, t, arm_span);
476            }
477            // !__m_done && (test_chain)
478            let not_done = Expr::new(ExprKind::Unary { op: UnaryOp::Not, value: Box::new(mk_ident(&done_name, arm_span)) }, arm_span);
479            let outer_cond = mk_binary(not_done, BinaryOp::And, test_chain, arm_span);
480
481            // arm body block:bind + guard + assign + done
482            let mut body_stmts = Vec::new();
483            collect_bindings(&pats[0], &mk_ident(&scrut_name, arm_span), &mut body_stmts, arm_span);
484            // 内层 body:__m_out = BODY; __m_done = true;
485            let inner_stmts = vec![mk_assign_stmt(&out_name, mk_any(body, arm_span), arm_span), mk_assign_stmt(&done_name, mk_value(Dynamic::Bool(true), arm_span), arm_span)];
486            let inner_block = Stmt::new(StmtKind::Block(inner_stmts), arm_span);
487            // 如果有 guard,再裹一层 if;否则直接展开
488            if let Some(g) = guard {
489                body_stmts.push(Stmt::new(StmtKind::If { cond: g, then_body: Box::new(inner_block), else_body: None }, arm_span));
490            } else {
491                body_stmts.push(inner_block);
492            }
493            let then_body = Stmt::new(StmtKind::Block(body_stmts), arm_span);
494            stmts.push(Stmt::new(StmtKind::If { cond: outer_cond, then_body: Box::new(then_body), else_body: None }, arm_span));
495        }
496        // 末尾求值:__m_out
497        stmts.push(Stmt::new(StmtKind::Expr(mk_any(mk_ident(&out_name, span), span), false), span));
498
499        Ok(Stmt::new(StmtKind::Block(stmts), span))
500    }
501
502    /// 在 stmt 顶层 peek 一下,判断接下来的 token 是不是 `import` 顶层
503    /// 声明(`import "name";` 或 `import "name", "path";`)。区分点:
504    /// 声明形式是 `import` 后跟空白+字符串字面量(`"`)或 ident;
505    /// 函数调用形式是 `import(...)`,`import` 后紧跟 `(` —— 这种仍走
506    /// 普通表达式路径(`import` ident + 调用)。`import` 关键字不进
507    /// KEYWORDS 列表就是为了让函数调用形式继续 work。
508    fn peek_import_top_level(&self) -> bool {
509        let rest = &self.buf[self.pos..];
510        let Some(after_kw) = rest.strip_prefix(b"import") else {
511            return false;
512        };
513        // import 后必须是空白
514        let Some(&first) = after_kw.first() else {
515            return false;
516        };
517        if !first.is_ascii_whitespace() {
518            return false;
519        }
520        // 跳过空白, peek 第一个非空白字符
521        let mut after_ws = after_kw.iter().skip_while(|b| b.is_ascii_whitespace());
522        matches!(after_ws.next(), Some(b'"'))
523    }
524
525    pub fn stmt(&mut self, is_pub: bool) -> Result<Stmt> {
526        self.check_fatal()?;
527        self.whitespace()?;
528        self.spans.push(self.pos);
529        let start = self.current_pos();
530        // 函数体内不允许 fn / struct / impl / const / static 顶层声明。
531        // 编译器对这些位置直接 panic，这里前置到 parser，让错误落到用户可见的地方。
532        if self.fn_body_depth > 0 {
533            for kw in &["fn", "struct", "impl", "const", "static"] {
534                if self.keyword(kw).is_ok() {
535                    return Err(anyhow!("函数体内不能定义 {}；请移到顶层或改用闭包", kw));
536                }
537            }
538        }
539        // impl body 允许 fn(方法)和 pub fn,但拒绝嵌套 struct / impl / const / static。
540        if self.impl_body_depth > 0 {
541            for kw in &["struct", "impl", "const", "static"] {
542                if self.keyword(kw).is_ok() {
543                    return Err(anyhow!("impl 体内不能定义 {}；请移到顶层", kw));
544                }
545            }
546        }
547        let stmt = if self.peek_import_top_level() {
548            // 顶层 import 声明:`import "module";` 或 `import "module", "path";`。
549            // 必须用 `peek` 而不是 `keyword`,因为 `import` 在 HEAD 下不
550            // 在 KEYWORDS 列表里 —— `import(...)` 函数调用形式仍要把
551            // `import` 当 ident 通过表达式解析路径走通。
552            // 区分要点:声明形式 `import` 后面是空白+字符串/ident;
553            // 函数调用形式 `import` 后面是 `(`。只在 stmt 顶层做这个判断。
554            if self.fn_body_depth > 0 || self.impl_body_depth > 0 {
555                return Err(anyhow!("import 只能作为顶层声明；请写在模块顶层"));
556            }
557            self.just("import").map_err(|_| anyhow!("expected import"))?;
558            self.whitespace()?;
559            let module = match self.get_expr()?.kind {
560                ExprKind::Value(Dynamic::String(value)) => value,
561                ExprKind::Ident(value) => value,
562                other => return Err(anyhow!("import 模块名必须是字符串或标识符，实际是 {:?}", other)),
563            };
564            self.whitespace()?;
565            let path = if self.take(b',').is_ok() {
566                self.whitespace()?;
567                match self.get_expr()?.kind {
568                    ExprKind::Value(Dynamic::String(value)) => value,
569                    ExprKind::Ident(value) => value,
570                    other => return Err(anyhow!("import 路径必须是字符串或标识符，实际是 {:?}", other)),
571                }
572            } else {
573                format!("{module}.zs").into()
574            };
575            self.until(b';')?;
576            Stmt::new(StmtKind::Import { module, path, is_pub }, Span::new(start, self.current_pos()))
577        } else if self.keyword("let").is_ok() {
578            let pat = self.pattern()?;
579            self.declare_pattern_symbols(&pat)?;
580            self.until(b'=')?;
581            self.whitespace()?;
582            let value = if self.get()? == b'{' {
583                if self.looks_like_dict() {
584                    self.get_expr()?
585                } else {
586                    // 块作为表达式:{ stmts; expr } 的值是最后一条语句的值。
587                    let span = self.current_pos();
588                    let block_stmt = self.block()?;
589                    Expr::new(ExprKind::Stmt(Box::new(block_stmt)), Span::new(span, self.current_pos()))
590                }
591            } else {
592                self.get_expr()?
593            };
594            self.whitespace()?;
595            let close = self.take(b';').is_ok();
596            let stmt = Stmt::new(StmtKind::Expr(value, close), Span::new(start, self.current_pos()));
597            Stmt::new(StmtKind::Let { pat, value: Box::new(stmt) }, Span::new(start, self.current_pos()))
598        } else if self.keyword("break").is_ok() {
599            self.until(b';')?;
600            Stmt::new(StmtKind::Break, Span::new(start, self.current_pos()))
601        } else if self.keyword("continue").is_ok() {
602            self.until(b';')?;
603            Stmt::new(StmtKind::Continue, Span::new(start, self.current_pos()))
604        } else if self.keyword("return").is_ok() {
605            self.whitespace()?;
606            let expr = if matches!(self.get(), Ok(b';' | b'}')) { None } else { Some(self.get_expr()?) };
607            self.whitespace()?;
608            if self.take(b';').is_err() && !matches!(self.get(), Ok(b'}')) {
609                self.until(b';')?;
610            }
611            Stmt::new(StmtKind::Return(expr), Span::new(start, self.current_pos()))
612        } else if self.keyword("if").is_ok() {
613            self.if_block()?
614        } else if self.keyword("loop").is_ok() {
615            Stmt::new(StmtKind::Loop(Box::new(self.block()?)), Span::new(start, self.current_pos()))
616        } else if self.keyword("while").is_ok() {
617            self.whitespace()?;
618            let cond = self.get_expr()?;
619            let body = Box::new(self.block()?);
620            Stmt::new(StmtKind::While { cond, body }, Span::new(start, self.current_pos()))
621        } else if self.keyword("for").is_ok() {
622            self.whitespace()?;
623            let pat = self.pattern()?;
624            self.whitespace()?;
625            self.keyword("in")?;
626            self.whitespace()?;
627            let range = self.get_expr()?;
628            self.push_decl_scope();
629            let result: Result<Stmt> = (|| {
630                self.declare_pattern_symbols(&pat)?;
631                let body = Box::new(self.block()?);
632                Ok(Stmt::new(StmtKind::For { pat, range, body }, Span::new(start, self.current_pos())))
633            })();
634            self.pop_decl_scope();
635            result?
636        } else if self.keyword("fn").is_ok() {
637            self.whitespace()?;
638            let (name, generic_params) = self.ident_generic()?;
639            self.declare_function_name(&name)?;
640            self.until(b'(')?;
641            let args = crate::parse_list!(self, Vec::new(), b')', b',', self.ident_typed()?);
642            let body = Box::new(self.function_body(&args)?);
643            Stmt::new(StmtKind::Fn { name, generic_params, args, body, is_pub }, Span::new(start, self.current_pos()))
644        } else if self.keyword("struct").is_ok() {
645            let (name, params) = self.ident_generic()?;
646            self.declare_symbol(&name)?;
647            if self.until(b'{').is_ok() {
648                let fields = crate::parse_list!(self, Vec::new(), b'}', b',', self.ident_typed()?);
649                if let Some(f) = fields.iter().find(|f| f.1.is_any()) {
650                    return Err(anyhow!("字段 {} 的类型未知", f.0));
651                }
652                Stmt::new(StmtKind::Struct { name, def: Type::Struct { params, fields }, is_pub }, Span::new(start, self.current_pos()))
653            } else {
654                self.until(b';')?;
655                Stmt::new(StmtKind::Struct { name, def: Type::Struct { params, fields: Vec::new() }, is_pub }, Span::new(start, self.current_pos()))
656            }
657        } else if self.keyword("const").is_ok() {
658            self.whitespace()?;
659            let (name, ty) = self.ident_typed()?;
660            self.declare_symbol(&name)?;
661            self.until(b'=')?;
662            let value = self.get_expr()?;
663            self.until(b';')?;
664            Stmt::new(StmtKind::Const { name, ty, value, is_pub }, Span::new(start, self.current_pos()))
665        } else if self.keyword("static").is_ok() {
666            self.whitespace()?;
667            let (name, ty) = self.ident_typed()?;
668            self.declare_symbol(&name)?;
669            self.whitespace()?;
670            if self.take(b'=').is_ok() {
671                let expr = self.get_expr()?;
672                self.until(b';')?;
673                Stmt::new(StmtKind::Static { name, ty, value: Some(expr), is_pub }, Span::new(start, self.current_pos()))
674            } else {
675                self.until(b';')?;
676                Stmt::new(StmtKind::Static { name, ty, value: None, is_pub }, Span::new(start, self.current_pos()))
677            }
678        } else if self.keyword("impl").is_ok() {
679            self.whitespace()?;
680            let target = self.get_type()?;
681            Stmt::new(StmtKind::Impl { target, body: Box::new(self.impl_body()?) }, Span::new(start, self.current_pos()))
682        } else if self.keyword("pub").is_ok() {
683            self.stmt(true)?
684        } else {
685            let expr = if self.get()? == b'{' {
686                if self.looks_like_empty_dict() {
687                    self.dict()?
688                } else if let Ok(block) = try_parse!(self, self.block()) {
689                    let _ = self.spans.pop();
690                    return Ok(block);
691                } else if let Ok(dict) = try_parse!(self, self.dict()) {
692                    dict
693                } else {
694                    let block = self.block()?;
695                    let _ = self.spans.pop();
696                    return Ok(block);
697                }
698            } else {
699                self.get_expr()?
700            };
701            self.whitespace()?;
702            if self.is_eof() {
703                Stmt::new(StmtKind::Expr(expr, false), Span::new(start, self.current_pos()))
704            } else if self.get()? == b';' {
705                self.pos += 1;
706                Stmt::new(StmtKind::Expr(expr, true), Span::new(start, self.current_pos()))
707            } else if self.get()? == b'}' {
708                Stmt::new(StmtKind::Expr(expr, false), Span::new(start, self.current_pos()))
709            } else {
710                return Err(anyhow!("未结束的表达式"));
711            }
712        };
713        let _ = self.spans.pop();
714        Ok(stmt)
715    }
716}
parser/stmt.rs

parser/
stmt.rs
